Method of creating pin fin surfaces for heat exchangers



S. HOLM METHOD OF CREATING PIN FIN SURFACES FOR HEAT EXCHANGERS Filed Aug. 10, 1948 Vf/V N01. M

INVENTOR.

Patented Apr. 25, 1950 METHOD OF CREATING PIN FIN sunracas FOR HEAT EXCHANGERS Sven Holm, Wellsvllle, N. Y., asslgnor to The All Preheater Corporation, New York, N. Y.

Application August 10, 1948, Serial No. 43,398

3 Claims. (Cl. 29-1573) The present invention relates to heat exchangers and particularly to a novel method for providing pin-like fins to serve as extended surface on plates that form walls of fluid passages.

In an earlier application Serial No. 752,008, filed June 3, 1947, in which applicant appears as a joint inventor, there is disclosed a plate or envelope type heat exchanger for exchanging heat between two confined fluids in which the efllciency of heat exchange is substantially increased by providing the walls of the fluid passages with a myriad of pin fins. The present invention involves a novel method of forming and attaching the pin fins to the walls of the fluid passages.

The invention will be best understood upon consideration of the following detailed description of an illustrative embodiment thereof when read in conjunction with the accompanying drawing in which:

Figure l is a plan view showing a plurality of parallelly disposed wires formed with zigzag loops together with metallic strips to which the Wires are to be attached.

Figure 2 is a fragmentary cross-sectional view through a pair of adjacent fluid passages in a heat exchanger wherein the passage walls are provided with extended surface and further illustrates a step in the process.

in an initial step of the process metallic wires of suitable diameter are bent to form therein a plurality of zigzag loops which as shown are of substantially rectangular alternately upright and inverted U-shape form. A plurality of these looped wires are laid parallel to each other in spaced relation, as on a flat surface. Then narrow metal strips ll, I2 are laid across each adjacent pair of wires so as to bridge the space between them, with the strips contacting the base portions it of the loops in one wire and the stretcher portions M of the inverted loops of the other wire of the pair. The metal strips l 1, l2 lie alternately beneath and upon the wires with which they are associated and when so arranged are attached to the latter as by welding or brazing. When the looped wires have been fastened to the metallic strips II and I2 the former are bent downwardly on fold lines A--A adjacent to the wires Ill and paralleling the longitudinal axis of the strip so as to form the strips into shallow channel members designated IS in Figure 2. The strips I2 are similarly bent, but in an upward direction on the fold lines B-B so that the alternate channels it Figure 2 become disposed at the bottom of the wire loops while the channel members l5 are disposed at the tops of the loops, considering the latter to be disposed in upright positions as shown in Figure 2. Thus each looped wire is attached by the stretcher portions M of its inverted loops to a channel member I 5 at a number of positions and the base portions l3 of its upright loops are similarly attached at numerous points to a channel member It which also is attached to a second looped wire at its opposite side. The assembled wires and channels are then disposed between two metallic plates 20 andi2l which are to form the walls of the fluid passage and by welding or brazing the channel members are bonded to these plates. If desired the base portions [3 and stretcher portions B4 of the looped wires may also be attached to the plates directly by bonding or welding. In the structure thus created the leg portions ll of the U-shaped loops constitute pinlike fins attached to the plates 2|] and 2| that form passage walls and constitute extended surface for the latter.

What I claim is: i

l. The method of making heat exchanger envelopes provided with extended surface which comprises; bending lengths of wire to form zigzag loops therein; disposing a plurality of such bent. wires of desired length in spaced parallel relation with their major axes located in the same plane; laying narrow metallic strips across the space between each pair of bent wires with the side edge portions of the strips contacting the base portions of the loops of one wire of a pair of contiguous wires and the corresponding head or stretcher portions of the loops of the otherwire of the said pair with said strips lying alternately upon and beneath the successive pairs: of wires; fastening the bent wires to said strips by welding or the like; bending both side edge portions of each strip along lines adjacent the wires attached thereto and parallel to its longitudinal axis to form channel members thereof having the bent wires attached to and extending along the legs of the channels, the strips being bent alternately downwardly and upwardly so that each wire is connected to adjacent channels in alternation at the base and stretcher portions of its loops; placing said channels together with their attached wires between spaced metallic plates with the latter contacting the base portions of said channels; and bending the channels and attached wires to said plates to form an envelope whereof the plates form walls and the leg portions of said loops constitute extended surface in the form of pin-like fins.

2. The method of making heat exchanger en- 3 velopes provided with extended surface whi comprises; bending lengths of wire to form zigzag loops therein of alternately upright and inverted substantially rectangular U-shaped form; disposing a plurality of such bent wires of desired length in spaced parallel relation with their major axes located in the same plane with the upright loops in adjacent strips in alinement; laying narrow metallic strips to span the gap between each pair of bent wires with the side edge portions of the strip alternately overlapping and underlying the base portions of the upright U-loops of one wire of a pair of contiguous wires and the corresponding head or stretcher portions of the inverted U-loops of the other wire of the said pair with said strips contacting the wires; fastening the bent wires to said strips by welding or the like; bending both side edge portions of each strip along lines adjacent the wires attached thereto and parallel to its longitudinal axis to form shallow channel members thereof having the bent wires attached to and extending.

along-the legs of the channels, the strips being bent alternately downwardly and upwardly so that all of the bent wires extend parallel to each other within planes parallel to the leg portions of said channels with adjacent wires being connected to an intermediate channel in alternation at the base and stretcher portions of their loops; placing said channels together with their at tached wires between a pair of spaced metallic plates with the latter contacting the base portions of said channels; and welding the channels and attached wires to said plates to form an envelope whereof the plates form walls and the leg portions of said loops constitute extended surface in the form of pin-like fins.

3. The method of makin heat exchanger envelopes provided with extended surface which comprises; bending lengths of wire to form zigverted substantially rectangular U-shaped form;

disposing a plurality of pairs of such bent wires of desired length in spaced parallel relation on a flat surface with the upright loops in adjacent strips in alinement; laying narrow metallic strips to span the gap between each pair of bent wires with the side edge portions of'the strips contacting the base portions of the upright U-loops of one wire of a pair of contiguous wires and the corresponding head or stretcher portions of the inverted U-loops of the other wire of the said pair with said strips lying alternately upon and beneath the successive pairs of wires; fastening the bent wires to said strips by welding or the like; bending both side edge portions of each strip adjacent the wires attached thereto along lines parallel to its longitudinal axis to form shallow U-shaped channel members thereof having the bent wires attached to and extending along the legs of the channels, the strips being bent alternately downwardly and upwardly, or vice versa, so that all of the bent wires extend parallel to each other within parallel planes with each wire being connected to adjacent channels in alternation at the base and stretcher portions of its loops; placing said channels together with their attached wires between spaced passage forming metallic plates with the latter contacting the base portions of said channels; and bonding the channels and attached wires to said plates.

' SVEN HOLM.

Name Date Still Sept. 14, 1937 Number 

